Autosomal dominant cerebellar ataxia (SCA6) associated with small polyglutamine expansions in the alpha 1A-voltage-dependent calcium channel

A polymorphic CAG repeat was identified in the human alpha 1A voltage-dependent calcium channel subunit. To test the hypothesis that expansion of this CAG repeat could be the cause of an inherited progressive ataxia, we genotyped a large number of unrelated controls and ataxia patients. Eight unrelated patients with late onset ataxia had alleles with larger repeat numbers (21-27) compared to the number of repeats (4-16) in 475 non-ataxia individuals. Analysis of the repeat length in families of the affected individuals revealed that the expansion segregated with the phenotype in every patient. We identified six isoforms of the human alpha 1A calcium channel subunit. The CAG repeat is within the open reading frame and is predicted to encode glutamine in three of the isoforms. We conclude that a small polyglutamine expansion in the human alpha 1A calcium channel is most likely the cause of a newly classified autosomal dominant spinocerebellar ataxia, SCA6.

Phenotypic heterogeneity of genomic disorders and rare copy-number variants

BACKGROUND

Some copy-number variants are associated with genomic disorders with extreme phenotypic heterogeneity. The cause of this variation is unknown, which presents challenges in genetic diagnosis, counseling, and management.

METHODS

We analyzed the genomes of 2312 children known to carry a copy-number variant associated with intellectual disability and congenital abnormalities, using array comparative genomic hybridization.

RESULTS

Among the affected children, 10.1% carried a second large copy-number variant in addition to the primary genetic lesion. We identified seven genomic disorders, each defined by a specific copy-number variant, in which the affected children were more likely to carry multiple copy-number variants than were controls. We found that syndromic disorders could be distinguished from those with extreme phenotypic heterogeneity on the basis of the total number of copy-number variants and whether the variants are inherited or de novo. Children who carried two large copy-number variants of unknown clinical significance were eight times as likely to have developmental delay as were controls (odds ratio, 8.16; 95% confidence interval, 5.33 to 13.07; P=2.11×10(-38)). Among affected children, inherited copy-number variants tended to co-occur with a second-site large copy-number variant (Spearman correlation coefficient, 0.66; P<0.001). Boys were more likely than girls to have disorders of phenotypic heterogeneity (P<0.001), and mothers were more likely than fathers to transmit second-site copy-number variants to their offspring (P=0.02).

CONCLUSIONS

Multiple, large copy-number variants, including those of unknown pathogenic significance, compound to result in a severe clinical presentation, and secondary copy-number variants are preferentially transmitted from maternal carriers. (Funded by the Simons Foundation Autism Research Initiative and the National Institutes of Health.).

Disruption of oxygen homeostasis underlies congenital Chuvash polycythemia

Chuvash polycythemia is an autosomal recessive disorder that is endemic to the mid-Volga River region. We previously mapped the locus associated with Chuvash polycythemia to chromosome 3p25. The gene associated with von Hippel-Lindau syndrome, VHL, maps to this region, and homozygosity with respect to a C-->T missense mutation in VHL, causing an arginine-to-tryptophan change at amino-acid residue 200 (Arg200Trp), was identified in all individuals affected with Chuvash polycythemia. The protein VHL modulates the ubiquitination and subsequent destruction of hypoxia-inducible factor 1, subunit alpha (HIF1alpha). Our data indicate that the Arg200Trp substitution impairs the interaction of VHL with HIF1alpha, reducing the rate of degradation of HIF1alpha and resulting in increased expression of downstream target genes including EPO (encoding erythropoietin), SLC2A1 (also known as GLUT1, encoding solute carrier family 2 (facilitated glucose transporter), member 1), TF (encoding transferrin), TFRC (encoding transferrin receptor (p90, CD71)) and VEGF (encoding vascular endothelial growth factor).

Mutation of TDP1, encoding a topoisomerase I-dependent DNA damage repair enzyme, in spinocerebellar ataxia with axonal neuropathy

Tyrosyl-DNA phosphodiesterase 1 (TDP1) repairs covalently bound topoisomerase I-DNA complexes and is essential for preventing the formation of double-strand breaks that result when stalled topoisomerase I complexes interfere with DNA replication in yeast. Here we show that a deficiency of this DNA repair pathway in humans does not predispose to neoplasia or dysfunctions in rapidly replicating tissues, but instead causes spinocerebellar ataxia with axonal neuropathy (SCAN1) by affecting large, terminally differentiated, non-dividing neuronal cells. Using genome-wide linkage mapping and a positional candidate approach in a Saudi Arabian family affected with autosomal recessive SCAN1, we identified a homozygous mutation in TDP1 (A1478G) that results in the substitution of histidine 493 with an arginine residue. The His493 residue is conserved in TDP1 across species and is located in the active site of the enzyme. Protein modeling predicts that mutation of this amino acid to arginine will disrupt the symmetric structure of the active site. We propose that loss-of-function mutations in TDP1 may cause SCAN1 either by interfering with DNA transcription or by inducing apoptosis in postmitotic neurons.

Mutant chromatin remodeling protein SMARCAL1 causes Schimke immuno-osseous dysplasia

Schimke immuno-osseous dysplasia (SIOD, MIM 242900) is an autosomal-recessive pleiotropic disorder with the diagnostic features of spondyloepiphyseal dysplasia, renal dysfunction and T-cell immunodeficiency. Using genome-wide linkage mapping and a positional candidate approach, we determined that mutations in SMARCAL1 (SWI/SNF2-related, matrix-associated, actin-dependent regulator of chromatin, subfamily a-like 1), are responsible for SIOD. Through analysis of data from persons with SIOD in 26 unrelated families, we observed that affected individuals from 13 of 23 families with severe disease had two alleles with nonsense, frameshift or splicing mutations, whereas affected individuals from 3 of 3 families with milder disease had a missense mutation on each allele. These observations indicate that some missense mutations allow retention of partial SMARCAL1 function and thus cause milder disease.

Risk of cancer in patients with dermatomyositis or polymyositis, and follow-up implications: a Scottish population-based cohort study

We conducted a national, retrospective population-based cohort study of 705 patients hospitalized with a first diagnosis of dermatomyositis (DM) or polymyositis (PM) during 1982-1996 based on linkage of hospital discharge, cancer registration, and death records in Scotland. Risks of cancer were assessed by calculating standardized incidence ratios (SIR). A first malignancy was diagnosed concurrently or subsequently in 50 patients with DM (SIR 7.7, 95% CI 5.7-10.1), and 40 patients with PM (2.1, 1.5-2.9). Significantly elevated risks were observed for lung, cervix uteri, and ovarian cancer in patients with DM, and for Hodgkin's disease in patients with PM. The excess risk of cancer was highest around the time of diagnosis, and for patients with DM remained high for at least 2 years. Risks were elevated for both sexes but only significantly so for females, and were highest in patients aged 45-74 years at the time of diagnosis for DM and 15-44 for PM.

Functional genetic analysis of mouse chromosome 11

Now that the mouse and human genome sequences are complete, biologists need systematic approaches to determine the function of each gene. A powerful way to discover gene function is to determine the consequence of mutations in living organisms. Large-scale production of mouse mutations with the point mutagen N-ethyl-N-nitrosourea (ENU) is a key strategy for analysing the human genome because mouse mutants will reveal functions unique to mammals, and many may model human diseases. To examine genes conserved between human and mouse, we performed a recessive ENU mutagenesis screen that uses a balancer chromosome, inversion chromosome 11 (refs 4, 5). Initially identified in the fruitfly, balancer chromosomes are valuable genetic tools that allow the easy isolation of mutations on selected chromosomes. Here we show the isolation of 230 new recessive mouse mutations, 88 of which are on chromosome 11. This genetic strategy efficiently generates and maps mutations on a single chromosome, even as mutations throughout the genome are discovered. The mutations reveal new defects in haematopoiesis, craniofacial and cardiovascular development, and fertility.

Genotype-Phenotype Correlation in NF1: Evidence for a More Severe Phenotype Associated with Missense Mutations Affecting NF1 Codons 844-848

Neurofibromatosis type 1 (NF1), a common genetic disorder with a birth incidence of 1:2,000-3,000, is characterized by a highly variable clinical presentation. To date, only two clinically relevant intragenic genotype-phenotype correlations have been reported for NF1 missense mutations affecting p.Arg1809 and a single amino acid deletion p.Met922del. Both variants predispose to a distinct mild NF1 phenotype with neither externally visible cutaneous/plexiform neurofibromas nor other tumors. Here, we report 162 individuals (129 unrelated probands and 33 affected relatives) heterozygous for a constitutional missense mutation affecting one of five neighboring NF1 codons-Leu844, Cys845, Ala846, Leu847, and Gly848-located in the cysteine-serine-rich domain (CSRD). Collectively, these recurrent missense mutations affect ∼0.8% of unrelated NF1 mutation-positive probands in the University of Alabama at Birmingham (UAB) cohort. Major superficial plexiform neurofibromas and symptomatic spinal neurofibromas were more prevalent in these individuals compared with classic NF1-affected cohorts (both p < 0.0001). Nearly half of the individuals had symptomatic or asymptomatic optic pathway gliomas and/or skeletal abnormalities. Additionally, variants in this region seem to confer a high predisposition to develop malignancies compared with the general NF1-affected population (p = 0.0061). Our results demonstrate that these NF1 missense mutations, although located outside the GAP-related domain, may be an important risk factor for a severe presentation. A genotype-phenotype correlation at the NF1 region 844-848 exists and will be valuable in the management and genetic counseling of a significant number of individuals.

Multiple CYP1B1 mutations and incomplete penetrance in an inbred population segregating primary congenital glaucoma suggest frequent de novo events and a dominant modifier locus

Primary congenital glaucoma (PCG) is an autosomal recessive disorder associated with unknown developmental defect(s) in the anterior chamber. Recently, we reported three distinct mutations in CYP1B1, the gene for cytochrome P4501B1, in 25 Saudi families segregating PCG. For this report, we analyzed 37 additional families and confirmed the initial finding of decreased penetrance. Mutations and intragenic single-nucleotide polymorphisms (SNPs) were also analyzed from direct sequencing of all CYP1B1 coding exons. Eight distinct mutations were identified: G61E, R469W and D374N, the most common Saudi mutations, account for 72, 12 and 7%, respectively, of all the PCG chromosomes. Five additional homozygous mutations (two deletions and three missense mutations) were detected, each in a single family. Affected individuals from five families had no CYP1B1 coding mutations, and each family had a unique SNP profile. The identification of eight distinct mutations in a single gene, on four distinct haplotypes, suggests a relatively recent occurrence of multiple mutations in CYP1B1 in Saudi Arabia. These data demonstrate decreased penetrance of the PCG phenotype in the Saudi population, because 40 apparently unaffected individuals in 22 families have mutations and haplotypes identical to their affected siblings. Two individuals were subsequently diagnosed with glaucoma and two others had abnormal ocular findings that are consistent with milder forms of glaucoma. Analysis of these 22 kindreds suggests the presence of a dominant modifier locus that is not linked genetically to CYP1B1. Linkage and Southern analyses excluded three candidate modifier loci.

What if cancer survival in Britain were the same as in Europe: how many deaths are avoidable?

Objective:

To estimate the number of deaths among cancer patients diagnosed in Great Britain that would be avoidable within 5 years of diagnosis if the mean (or highest) survival in Europe for patients diagnosed during 1985–1989, 1990–1994 and 1995–1999 were achieved.

Design:

Five-year relative survival for cancers in Great Britain compared with that from other countries in the EUROCARE-2, -3 and -4 studies. Calculation of excess deaths (those more than expected from mortality in the general population) that would be avoidable among cancer patients in Britain if relative survival were the same as in Europe.

Setting:

Great Britain (England, Wales, Scotland) and 13 other European countries.

Subjects:

2.8 million adults diagnosed in Britain with 1 of 39 cancers during 1985–1989 (followed up to 1994), 1990–1994 (followed up to 1999) and 1995–1999 (followed up to 2003).

Main outcome measure:

Annual number of avoidable deaths within 5 years of diagnosis. Percentage of the excess (cancer-related) deaths among cancer patients that would be avoidable.

Results:

Compared with the mean European 5-year relative survival, the largest numbers of avoidable deaths for patients diagnosed during 1985–1989 were for cancers of the breast (about 18% of the excess mortality from this cancer, 7541 deaths), prostate (14%, 4285), colon (9%, 4090), stomach (8%, 3483) and lung (2%, 3548). For 1990–1994, the largest numbers of avoidable deaths were for cancers of the prostate (20%, 7335), breast (15%, 6165), colon (9%, 4376), stomach (9%, 3672), lung (2%, 3735) and kidney (22%, 2644). For 1995–1999, most of the avoidable deaths were for cancers of the prostate (17%, 5758), breast (15%, 5475), lung (3%, 4923), colon (10%, 4295), stomach (9%, 3137) and kidney (21%, 2686).

Overall, some 6600–7500 premature deaths would have been avoided each year among cancer patients diagnosed in Britain during 1985–1999 if the mean survival in Europe had been achieved. This represents 6–7% of cancer-related mortality. Compared with the highest European survival, avoidable premature mortality among cancer patients fell from about 12 800 deaths a year (12.2% of cancer-related mortality) to about 11 400 deaths a year (10.6%) over the same period.

A large component of the avoidable mortality is due to prostate cancer: excluding this cancer from comparison with the European mean survival reduces the annual number of avoidable deaths by 1000–1500, and the percentage of excess mortality by up to 1%. Compared with the highest survival, the annual number of avoidable deaths would be 1500–2000 fewer, and 1–2% lower as a percentage of excess mortality, but the overall trend in avoidable premature mortality among cancer patients would be similar, falling from 11.4% (1985–1989) to 10.3% (1990–1994) and 9.7% for those diagnosed during 1995–1999.

For several cancers, survival in Britain was slightly higher than the mean survival in Europe; this represented some 110–180 premature deaths avoided each year during the period 1985–2003.

Conclusions:

Avoidable premature mortality among cancer patients diagnosed in Britain during 1985–1999 has represented 6–7% of cancer-related mortality compared with the mean survival in Europe. Compared with the highest levels of survival in Europe, the reduction from 12.2% to 10.6% of cancer-related mortality reflects small but steady progress over the period 1985–2003.

The fibroblast growth factor receptor-4 Arg388 allele is associated with prostate cancer initiation and progression

PURPOSE

Increased expression of fibroblast growth factors that can activate the fibroblast growth factor receptor-4 (FGFR-4) occurs in a substantial fraction of human prostate cancers in vivo. A germline polymorphism of the FGFR-4 gene resulting in expression of arginine at codon 388 (Arg388) is associated with aggressive disease in patients with breast and colon cancer. We therefore sought to determine whether the FGFR-4 Arg388 allele was associated with prostate cancer incidence and/or the occurrence of aggressive disease.

EXPERIMENTAL DESIGN

The FGFR-4 genotype of men undergoing radical prostatectomy and controls of the same race was determined and the genotype correlated with clinical and pathologic markers of disease aggressiveness. PNT1A cell lines expressing predominantly the FGFR-4 Arg388 or Gly388 allele were established, and cell migration and invasiveness of these cells were assessed by a wounding assay and by quantitative determination of invasion through Matrigel. Expression of urokinase-type plasminogen activator receptor was determined by quantitative RT-PCR and enzyme-linked immunoabsorption assay.

RESULTS

Homozygosity for the FGFR-4 Arg388 allele is strongly associated with the occurrence of prostate cancer in white men. The presence of the FGFR-4 Arg388 allele is also correlated with the occurrence of pelvic lymph node metastasis and biochemical (prostate-specific antigen) recurrence. Expression of FGFR-4 Arg388 in immortalized prostatic epithelial cells results in increased cell motility and invasion through Matrigel and was associated with increased expression of urokinase-type plasminogen activator receptor.

CONCLUSION

The FGFR-4 Arg388 allele is associated with both an increased incidence and clinical aggressiveness of prostate cancer and results in changes in cellular motility and invasiveness in immortalized prostate epithelial cells consistent with the promotion of metastasis.

Haploinsufficiency of PAX9 is associated with autosomal dominant hypodontia

We recently identified a frame-shift mutation in the PAX9 gene as the underlying cause for hypodontia involving permanent molar teeth segregating in an autosomal dominant pattern in a single large family (Stockton et al. 2000). Here we report a small nuclear family in which a father and his daughter are affected with severe hypodontia, involving agenesis of all primary and permanent molars, evidently caused by deletion of the entire PAX9 gene. Hemizygosity at the PAX9 locus in the two affected individuals was initially discovered when an informative single nucleotide polymorphism, identified while sequencing the gene for mutations, appeared to demonstrate non-Mendelian inheritance. Fluorescence in situ hybridization (FISH) analysis with a cosmid containing the PAX9 gene yielded a signal on only one chromosome 14 homologue and confirmed the presence of a deletion encompassing the PAX9 locus. Analysis of microsatellite loci in the vicinity of PAX9 delineated one breakpoint of the deletion. These data, in concert with FISH analysis with cosmids encompassing a 199 kb region, indicated that the deletion is between approximately 44 kb and 100 kb. PAX9 is one of two genes, and the only odontogenic gene within the deletion interval, thus supporting the model of haploinsufficiency for PAX9 as the underlying basis for hypodontia.

A mixed epigenetic/genetic model for oligogenic inheritance of autism with a limited role for UBE3A

The genetic contribution to autism is often attributed to the combined effects of many loci (ten or more). This conclusion is based in part on the much lower concordance for dizygotic (DZ) than for monozygotic (MZ) twins, and is consistent with the failure to find strong evidence for linkage in genome-wide studies. We propose that the twin data are compatible with oligogenic inheritance combined with a major, genetic or epigenetic, de novo component to the etiology. Based on evidence that maternal but not paternal duplications of chromosome 15q cause autism, we attempted to test the hypothesis that autism involves oligogenic inheritance (two or more loci) and that the Angelman gene (UBE3A), which encodes the E6-AP ubiquitin ligase, is one of the contributing genes. A search for epigenetic abnormalities led to the discovery of a tissue-specific differentially methylated region (DMR) downstream of the UBE3A coding exons, but the region was not abnormal in autism lymphoblasts or brain samples. Based on evidence for allele sharing in 15q among sib-pairs, abnormal DNA methylation at the 5'-CpG island of UBE3A in one of 17 autism brains, and decreased E6-AP protein in some autism brains, we propose a mixed epigenetic and genetic model for autism with both de novo and inherited contributions. The role of UBE3A may be quantitatively modest, but interacting proteins such as those ubiquitinated by UBE3A may be candidates for a larger role in an oligogenic model. A mixed epigenetic and genetic and mixed de novo and inherited (MEGDI) model could be relevant to other "complex disease traits".

Clonal hematopoiesis in familial polycythemia vera suggests the involvement of multiple mutational events in the early pathogenesis of the disease

Familial clustering of malignancies provides a unique opportunity to identify molecular causes of cancer. Polycythemia vera (PV) is a myeloproliferative disorder due to an unknown somatic stem cell defect that leads to clonal myeloid hyperproliferation. We studied 6 families with PV. The familial predisposition to PV appears to follow an autosomal dominant inheritance pattern with incomplete penetrance. All examined females informative for a transcriptional clonality assay had clonal hematopoiesis. We excluded linkage between PV and a number of previously proposed candidate disease loci (c-mpl, EPOR, 20q, 13q, 5q, 9p). Therefore, mutations at these loci are unlikely primary causes of familial PV. The finding of erythropoietin-independent erythroid progenitors in healthy family members indicated the presence of the PV stem cell clone in their hematopoiesis. This finding, together with clonal hematopoiesis in the affected individuals, supports the hypothesis of multiple genetic defects involved in the early pathogenesis of PV.

Endemic polycythemia in Russia: mutation in the VHL gene

Chuvash polycythemia (CP) is an autosomal recessive condition that is endemic in the Russian mid-Volga River region of Chuvashia. We previously found that CP patients may have increased serum erythropoietin (EPO) levels, ruled out linkage to both the EPO and EPO receptor (EPOR) gene loci, and hypothesized that the defect may lie in the oxygen homeostasis pathway. We now report a study of five multiplex Chuvash families which confirms that CP is associated with significant elevations of serum EPO levels and rules out a location for the CP gene on chromosome 11 as had been reported by other investigators or a mutation of the HIF-1 alpha gene. Using a genome-wide screen, we localized a region on chromosome 3 with a LOD score >2. After sequencing three candidate genes, we identified a C to T transition at nucleotide 598 (an R200W mutation) in the von Hippel-Lindau (VHL) gene. The VHL protein (pVHL) downregulates the alpha subunit of hypoxia-inducible factor 1 (HIF-1 alpha), the main regulator of hypoxia adaptation, by targeting the protein for degradation. In the simplest scenario, disruption of pVHL function causes a failure to degrade HIF-1 alpha resulting in accumulation of HIF-1 alpha, upregulation of downstream target genes such as EPO, and the clinical manifestation of polycythemia. These findings strongly suggest that CP is a congenital disorder of oxygen homeostasis.

Update of PAX2 mutations in renal coloboma syndrome and establishment of a locus-specific database

Renal coloboma syndrome, also known as papillorenal syndrome is an autosomal-dominant disorder characterized by ocular and renal malformations. Mutations in the paired-box gene, PAX2, have been identified in approximately half of individuals with classic findings of renal hypoplasia/dysplasia and abnormalities of the optic nerve. Prior to 2011, there was no actively maintained locus-specific database (LSDB) cataloguing the extent of genetic variation in the PAX2 gene and phenotypic variation in individuals with renal coloboma syndrome. Review of published cases and the collective diagnostic experience of three laboratories in the United States, France, and New Zealand identified 55 unique mutations in 173 individuals from 86 families. The three clinical laboratories participating in this collaboration contributed 28 novel variations in 68 individuals in 33 families, which represent a 50% increase in the number of variations, patients, and families published in the medical literature. An LSDB was created using the Leiden Open Variation Database platform: www.lovd.nl/PAX2. The most common findings reported in this series were abnormal renal structure or function (92% of individuals), ophthalmological abnormalities (77% of individuals), and hearing loss (7% of individuals). Additional clinical findings and genetic counseling implications are discussed.

Expanding the phenotype of alveolar capillary dysplasia (ACD)

OBJECTIVES

To define the phenotype of congenital alveolar capillary dysplasia (ACD) as a first step toward mapping the responsible gene(s).

STUDY DESIGN

Analysis of pathology reports and microscopic slides of 23 subjects with ACD and sequence analysis of two candidate genes.

RESULTS

Our review of the pre- and postmortem records delineates both the natural history of this condition and the associated anomalies. Our collection of families corroborates the likely autosomal recessive nature of this condition in some families and provides additional data for genetic and prenatal counseling. Anomalies of many organ systems were detected either in the prenatal period or during the hospital course. However, some major anomalies were not detected until postmortem examination. Left-right asymmetry and gastrointestinal malrotation emerge as important, previously recognized but underappreciated phenotypic features of ACD. Finally, we used sequence analysis to exclude mutations in the coding region of two candidate genes, bone morphogenetic protein type II receptor (BMPR2) and endothelial monocyte-activating polypeptide II (EMAP II), as candidates for ACD.

CONCLUSIONS

Understanding the clinical spectrum of ACD and the cloning of an "ACD gene" both have implications for counseling, for prenatal testing, and for understanding the molecular pathophysiology of ACD and other organ malformations that are associated with this condition.

Forewarned is forearmed--benefits of preparatory information on video cassette for patients receiving chemotherapy or radiotherapy--a randomised controlled trial

A series of UK and European audits have revealed that a high proportion of patients remain dissatisfied with the information they received following a diagnosis of cancer. Additional educational aids are often required to facilitate the consent process, and our previous work showed a high level of acceptability for video-directed information for this purpose. In this study a multidisciplinary team of health professionals worked with patients, a documentary film company and experienced television personalities to produce an information film. The aim of this study was to assess the benefits of receiving a cassette to take home following the first consultation and this was evaluated in a randomised multicentre controlled study among 220 patients receiving chemotherapy or radiotherapy over a 6-month period. There was a significant correlation between satisfaction and reduced treatment-related anxiety overall. In the video group, the mean Hospital Anxiety and Depression (HAD) anxiety score was significantly lower during treatment compared with the non-video group (4.6+/-3.7 (range: 0-18) versus 7.4+/-5.2 (range: 0-20), Chi square test P=0.001). Likewise, the mean HAD depression scores were also significantly lower in the patients prepared for the side-effects of treatment with the video (2.9+/-2.9 (range: 0-13) versus 5.3+/-4.7 (range: 0-21) Chi square test P=0.001). 81% felt the video was helpful, only 5% of patients felt this extra information was worrying. Well designed video cassettes should be regarded as a useful additional information strategy, within routine oncology practice.

Parental occupation at periconception: findings from the United Kingdom Childhood Cancer Study

AIMS

To study the risk of childhood cancer in relation to parental occupation and related exposures.

METHODS

Self reported occupational data from mothers and fathers of 3838 children with cancer and 7629 control children were analysed. Odds ratios were calculated for 31 "occupational groups" by parent, diagnostic group (leukaemia, acute lymphoblastic leukaemia (ALL), central nervous system tumours, and other cancers) and time of exposure (periconception, birth, and diagnosis).

RESULTS

Findings did not support the hypothesis that occupational exposure of fathers to ionising radiation increases the risk of childhood cancer in their offspring. Specific examination of periconceptual chemical exposures showed small but statistically significant increased risks for leukaemia and ALL among children whose fathers were exposed to exhaust fumes, driving, and/or inhaled particulate hydrocarbons. In the remaining analyses, a fourfold increase in the risk of other cancers was observed among the children of fathers working with leather but based on small numbers. Both maternal and paternal exposure to textile dust was related to an increased risk of other cancers.

CONCLUSION

Results failed to produce any strong evidence to link parental occupational exposures with an increased risk of childhood cancer. No relation was found for paternal periconceptual exposure to ionising radiation. The consistency of the associations observed between childhood leukaemia and paternal occupational exposure to exhaust fumes, driving, and/or inhaled particulate hydrocarbons at periconception suggest a small risk for vehicle related exhaust. However, other explanations cannot be excluded and further research into the nature of the associations is required.

Clinical spectrum of individuals with pathogenic NF1 missense variants affecting p.Met1149, p.Arg1276, and p.Lys1423: genotype-phenotype study in neurofibromatosis type 1

We report 281 individuals carrying a pathogenic recurrent NF1 missense variant at p.Met1149, p.Arg1276, or p.Lys1423, representing three nontruncating NF1 hotspots in the University of Alabama at Birmingham (UAB) cohort, together identified in 1.8% of unrelated NF1 individuals. About 25% (95% confidence interval: 20.5-31.2%) of individuals heterozygous for a pathogenic NF1 p.Met1149, p.Arg1276, or p.Lys1423 missense variant had a Noonan-like phenotype, which is significantly more compared with the "classic" NF1-affected cohorts (all p < .0001). Furthermore, p.Arg1276 and p.Lys1423 pathogenic missense variants were associated with a high prevalence of cardiovascular abnormalities, including pulmonic stenosis (all p < .0001), while p.Arg1276 variants had a high prevalence of symptomatic spinal neurofibromas (p < .0001) compared with "classic" NF1-affected cohorts. However, p.Met1149-positive individuals had a mild phenotype, characterized mainly by pigmentary manifestations without externally visible plexiform neurofibromas, symptomatic spinal neurofibromas or symptomatic optic pathway gliomas. As up to 0.4% of unrelated individuals in the UAB cohort carries a p.Met1149 missense variant, this finding will contribute to more accurate stratification of a significant number of NF1 individuals. Although clinically relevant genotype-phenotype correlations are rare in NF1, each affecting only a small percentage of individuals, together they impact counseling and management of a significant number of the NF1 population.

Phenotypic characterization of Bbs4 null mice reveals age-dependent penetrance and variable expressivity

Bardet-Biedl syndrome (BBS) is a rare oligogenic disorder exhibiting both clinical and genetic heterogeneity. Although the BBS phenotype is variable both between and within families, the syndrome is characterized by the hallmarks of developmental and learning difficulties, post-axial polydactylia, obesity, hypogenitalism, renal abnormalities, retinal dystrophy, and several less frequently observed features. Eleven genes mutated in BBS patients have been identified, and more are expected to exist, since about 20-30% of all families cannot be explained by the known loci. To investigate the etiopathogenesis of BBS, we created a mouse null for one of the murine homologues, Bbs4, to assess the contribution of one gene to the pleiotropic murine Bbs phenotype. Bbs4 null mice, although initially runted compared to their littermates, ultimately become obese in a gender-dependent manner, females earlier and with more severity than males. Blood chemistry tests indicated abnormal lipid profiles, signs of liver dysfunction, and elevated insulin and leptin levels reminiscent of metabolic syndrome. As in patients with BBS, we found age-dependent retinal dystrophy. Behavioral assessment revealed that mutant mice displayed more anxiety-related responses and reduced social dominance. We noted the rare occurrence of birth defects, including neural tube defects and hydrometrocolpos, in the null mice. Evaluations of these null mice have uncovered phenotypic features with age-dependent penetrance and variable expressivity, partially recapitulating the human BBS phenotype.

Retinal degeneration associated with RDH12 mutations results from decreased 11-cis retinal synthesis due to disruption of the visual cycle

Retinoid dehydrogenases/reductases catalyze key oxidation-reduction reactions in the visual cycle that converts vitamin A to 11-cis retinal, the chromophore of the rod and cone photoreceptors. It has recently been shown that mutations in RDH12, encoding a retinol dehydrogenase, result in severe and early-onset autosomal recessive retinal dystrophy (arRD). In a cohort of 1011 individuals diagnosed with arRD, we have now identified 20 different disease-associated RDH12 mutations, of which 16 are novel, in a total of 22 individuals (2.2%). Haplotype analysis suggested a founder mutation for each of the three common mutations: p.L99I, p.T155I and c.806_810delCCCTG. Patients typically presented with early disease that affected the function of both rods and cones and progressed to legal blindness in early adulthood. Eleven of the missense variants identified in our study exhibited profound loss of catalytic activity when expressed in transiently transfected COS-7 cells and assayed for ability to convert all-trans retinal to all-trans retinol. Loss-of-function appeared to result from decreased protein stability, as expression levels were significantly reduced. For the p.T49M variant, differing activity profiles were associated with each of the alleles of the common p.R161Q RDH12 polymorphism, suggesting that genetic background may act as a modifier of mutation effect. A locus (LCA3) for Leber congenital amaurosis, a severe, early-onset form of arRD, maps close to RDH12 on chromosome 14q24. Haplotype analysis in the family in which LCA3 was mapped excluded RDH12 as the LCA3 gene and thus suggests the presence of a novel arRD gene in this region.

Evidence for an association between cutaneous malignant melanoma and lymphoid malignancy: a population-based retrospective cohort study in Scotland

We analysed the risk of cutaneous malignant melanoma (CM) occurring in patients following a diagnosis of non-Hodgkin's lymphoma (NHL) or chronic lymphatic leukaemia (CLL), and of NHL or CLL subsequently developing in CM survivors. Cohorts of patients with CM, NHL or CLL (index cancer) diagnosed between 1975 and 1997 were identified from the Scottish national cancer registry and followed through the registry for subsequent CM, NHL or CLL. The standardised incidence ratio (SIR) for each cancer was calculated and overall risk, risk in relation to gender and age at diagnosis of the index cancers and time from diagnosis of the index cancer to the diagnosis of the second malignancy were measured. There were 9385 CM patients, 4016 CLL patients and 13 857 NHL patients identified with an index cancer with 56 195, 14 450 and 44 999 person-years of follow-up, respectively. There was an increased risk of both CLL and NHL following a diagnosis of CM (SIR 2.3 and 1.5, respectively) and of CM following a diagnosis of CLL and NHL (SIR 2.3 and 2.1, respectively). The risk was statistically significantly increased for CLL developing in CM patients and for CM occurring in NHL survivors (P<0.05). This study supports an association between CM, CLL and NHL developing in the same patient. Immunosuppression, exposure to ultraviolet radiation and genetic factors may lead to a host environment that is conducive to the development of these malignancies.

Newfoundland rod-cone dystrophy, an early-onset retinal dystrophy, is caused by splice-junction mutations in RLBP1

Some isolated populations exhibit an increased prevalence of rare recessive diseases. The island of Newfoundland is a characteristic geographic isolate, settled by a small number of families primarily during the late 1700s and early 1800s. During our studies of this population, we identified a group of families exhibiting a retinal dystrophy reminiscent of retinitis punctata albescens but with a substantially lower age at onset and more-rapid and distinctive progression, a disorder that we termed "Newfoundland rod-cone dystrophy" (NFRCD). The size of one of these families was sufficient to allow us to perform a genomewide screen to map the NFRCD locus. We detected significant linkage to markers on the long arm of chromosome 15, in a region encompassing RLBP1, the gene encoding the cellular retinaldehyde-binding protein. Previously, mutations in RLBP1 have been associated with other retinal dystrophies, leading us to hypothesize that RLBP1 mutations might also cause NFRCD. To test this hypothesis, we sequenced all coding exons and splice junctions of RLBP1. We detected two sequence alterations, each of which is likely to be pathogenic, since each segregates with the disease and is predicted to interfere with mRNA splicing. In contrast to some previously reported RLBP1 mutations, which yield a protein that may retain some residual activity, each NFRCD mutation is likely to give rise to a null allele. This difference may account for the severe phenotype in these families and exemplifies the molecular continuum that underlies clinically distinct but genetically related entities.